VIDIOC_QUERYSTD — Sense the video standard received by the current input
int ioctl( | int fd, |
| int request, | |
v4l2_std_id *argp); |
The hardware may be able to detect the current video
standard automatically. To do so, applications call
VIDIOC_QUERYSTD with a pointer to a v4l2_std_id type. The
driver stores here a set of candidates, this can be a single flag or a
set of supported standards if for example the hardware can only
distinguish between 50 and 60 Hz systems. If no signal was detected,
then the driver will return V4L2_STD_UNKNOWN. When detection is not
possible or fails, the set must contain all standards supported by the
current video input or output.
On success 0 is returned, on error -1 and the errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.
Standard video timings are not supported for this input or output.